the .cert and .key files I generated with easy-rsa on a windows PC were loaded in the RUT240, no error message, and I build up a .ovpn file using the ca and the clients .crt and .key files.
I can not figure out, which version of OpenVPN is able to work with RUT240. My FW is the latest I get from Teltonika web page.
I found out, that the newest OpenVPN software (now called OpenVPN Connect) didn't install easy-rsa. This should be noted down in the article. You have to install an older version or you should get easy-rsa from another source. And, which version of easy-rsa is the correct one to work with RUT240. I think, the article needs some updates !!!
First I tried to establish TAP with TCP, failed I tried TAP with UDP, failed but error looks different. Then I tried TUN and UDP but I do some missconfiguration and my RUT 240 crashed.
I do a reset to factory defaults now (first time with new FW) and start over again.
I will provide the infos asap.
With best regards